Tuning means



Dec. 13, 1949 R. G. scHRlEf-'ER 2,490336 TUNING MEANS Filed Oct. 10,` 1944 2 Sheets-Sheet l wucwto ROBERT G. SCHRIEFER Dc- 13, 1949 R. G. scHRlEl-'ER 2490,836

TUNING MEANS Filed Oct. 10, 1944 2 Sheets-Sheet 2 ROBERT G. SCHRIEFER Patentea Dec. 13, 1949 UNITED STATES PATENT OFFICE TUNING MEAN S Robert G. Schrefer, Fort Wayne, Ind.

Application October 10, 1944, Serial No. 558,069

13 Claims. (Cl. 250-110) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) This invention relates to the tuning of resonant circuits and more particularly to such circuits, adapted to be tuned through an unusually wide band of ultra high frequencies.

In the art to which this invention pertains lt has' been the custom to tune the resonant circuits through a limited band by means of a variable condenser and to alter the inductance of the circuit in Steps to shift to an adjacent band. Alternatively, the value of the inductance has been varied continucusly as by means of sliders. Each of these methods requires the use of leads, the lengths of which will vary from time to time.

I-Iowever, in this art, it is necessary to decrease the length of the leads as much as possible in order to permit obtaining the low inductance necessary to get the ultra high frequency desired. Furthermore the radiation of the tuning circuits should be reduced as much as possible. It is therefore seen that the old methods do not operate to full advantage in that they require the use of undesirably long leads which will be too long to permit the higher frequencies being readily obtained.

Another disadvantage of the old methods is that unbalance of the L/C ratio gives less than optimum response to currents at the resonant frequency, as the tank circuit is tuned and the I gain varies widely throughout the band of frequencies.

Furthermore, when the frequency of the oscillatory circuit is varied by means of the usual variable inductance, as to make large changes, the leads involved must of necessity be unbalanced for at least some part of the entire band, which will result in the undesired radiation of energy when Operating in that particular part of the band.

Therefore, it is an object of this invention to provide a tuning device for an oscillatory circuit which will permit tuning over an unusually large frequency band.

It is an ancillary object of this invention to provide 'a tuning device of the type described which shall not necessitate the' use of sliders, contacts or of tapped inductances.

Another object of this invention is the provision of a device which will permit tuning through the wide band and maintaining a constant L/ C ratio.

Still another object of this invention is the provision of a tuning device which will permit substantially uniform gain while being tuned through a wide frequency band.

A still further object of this invention is to invention, reference for the 2 provide a device of the type described which shall have symmetrical leads throughout its entire range and will have balanced currents and vcltages at all times and will not produce undesired radiations.

Yet another object of this invention is to provide a circuit which shall have the shortest possible leads in order to produce oscillation of very short wavelengths.

In order to accomplish the object of this invention there is provided an inductance loop having a condenser stator connected directly to each end thereof. A single shaft is disposed in symmetrical relation to the inductance loop and to the two stators at right angles to the axis of the inductance. Mounted on the said shaft is a structure composed preferably of three or more metallic shading plates adapted to be rotated from a position parallel to the axis of the inductance to a position which is co-planar with the center of the inductance coil. Also mounted on the shaft is a condenser rotor having double plates, adapted to cooperate with each of the said stators.

The two stators are connected to the plate and grid respectively of a high frequency type tube such for instance as a door knob tube. The connection to the grid may be through a small condenser as will be described later. The midpoint portion of the inductance is connected to a high voltage source and through a condenser to ground. The rotor plates of the double variable condenser which has been described are adjusted relative to the shading plates so that when the inductance is at minimum value the rotor plates of each half of he double condenser will be out of the stators and the value of the condensei` will be minimum.

Other objects and features of the present invention will appear more fully hereinafter upon consideration of the accompanying vdrawings which disclose one embodiment of the invention.

`It is expressly understood, however, that the drawings are designed for purposes of illustration only and not as a definition of the limits ofl `the .latter purpose being had to the appended claims. -v

In the drawings, wherein similar reference characters denote similar elements throughout the several views:

Fig. 1 is a plan view of a tuning apparatus constructed in accordance with the principles of the present invention;

Fig. 2 is an elevation view of the apparatus shown in Fig. 1;

Vinductor l-.

ductor iii shown in the form of an open, ,single4 metallic loop, constructed of bus bar material for example. The inductor IO is supported in ra' horizontal plane by means `of suitable insulators mounted on a supporting base B2 which may comprise the bottom panel of the apparatus with which the tuning device is connected.

The tuning device further comprises a variable.

condenser 14 including a pair of multiplate' stators 15 and IB, and a multi-plate rotor 'adapted to cooperate with the stators |5 and [6 v'varying degrees of capacitive relationship. 'The condenser statcrs l' and E5 are respectively secured to the open ends of the inductor Hi, and

the rotor ll is supported on one end of a shaft f '18, positioned traversely of the inductor W, to maintain the aforeinentioned relationship. The shaft is rotatably mounted in the position disclosed by means of a bearing supporting mem- 'ber 1'9, located adjacent the condenser 14, and

a journal fis provided at the mid-point of the The shaft E8 passes through the Ffront panel 2i of the apparatus and a control 'knob 22 is positioned on the extended end thereof to provide a means for imparting rotation i Vthereto.

An inductor tuning member '23 is mounted on 'the shaft la for rotation therewith to vary the inductance of the induc'tor iii. The inductor tun-J ing member 23 is shown including a plurality of 'metallic shading plates 24 separated from each other by spaces 25 of insulating material. The Vtuning member 23 is of substantially circular configuration and is mounted for rotation within the inductor IB. the tuning .member 23 is in the position depicted 'in Figs. 1 and 2 of the drawings, the inductor Hi is tuned to vmaximum inductance, whereas, when `the shaft 18 is rotated so 'that the metallic shading plates 24 are in the plane of the in- Vductor W, a minimum Value of inductance is offered.

As mentioned heretofore, it is an object of the present invention to provide a tuning device characterized in such a 'manner as to permit tun- 'ing throughout an unusually wide frequency band while maintainin'g a constant inductance to capacitance ratio. The foregoing is accomplished by the variable inductor-capacitor ar- 'rangement of Figs. 1 and 2, With the tuning vmember 23 and the 'rotor i? mounted in pretWeen inductive reactance and capacitance reactance is maintained 'substantially constant throughout the extremely wide frequency band of the tuning device.

*fn order to .couple 'the tuning device to a useful circuit, to form an oscillatory circuit for ex- With this arrangement, when.

4 ample, connection blocks 26 and 27 are respectively provided on the condenser stators E5 and it. For a purpose that will appear more fully hereinafter, the connection block 27 is spaced from the condenser stator Hi by a strip of insulating material 28 to thereby form a capacitive coupling. ,In Fig. 1 the connection blocks 26 and 'il' are shown respectively coupled to the anode 29 and to the control electrode 36 of an electron discharge device 3! which may be of .the door knob type.

in Fig. 3 of the drawings the Fig. 1 device is disclosed in circuit form. A tuned circuit 32, including an inductance 33 and the capacitance between the stators 34-35, corresponds to the 'tuned circuit formed by the inductor lo and the condenser E4 of Fig. l. The stator 34 is connected to the control electrode 3G through a coupling capacitance 3G, corresponding to the capacitance established by the strip of insulating 'material 23 of Pig. 1, and the stator 35 is di- `rect'ly :connected to the anode 29. The 'capacitance between 'the stators 34-35 is varied by intermediate tuning element I37, and the value of the inductance 33 is determined by a shortcircuited secondary 38 including an inductance Lie inductively coupled to the inductance 33. rEhe tuning element 37 and the short-circuited secondary 38 respectively correspond to the rotor il'i Vand the inductor tuning member 23 Vof Fig. 1,. As indicated in Fig. 3, the 'tuning element ''i and the short-circuited secondary 38 are ganged together to simultaneously Vary the capacitance and the inductance of the vtuned circuit 32,. And .it is expressly understood that the capacitance and inductance are varied in the i predetermined relation described heretofore.

In Fig. 4 of the drawings the present invention is disclosed in connection with a conventionaloscillator circuit .of .the 'Hartley type. This oscillator includes an electron `discharge device 'to 'having Van anode 4,a cathodelfz and a control electrode 43, coupled to a. 'tuned circuit .44. The tuned circuit 44 includes a variable inductance 45 and a variable capacitance 46 constructed and .simu'ltaneously tuned 'in a manner' described heretofore.

It will be seen from the foregoing that by the means provided not only may'the characteristics of the -oscillatory circuit be varied through extremely wide limits from the condition in which there is minimum inductance .and minimum capacity to that in which there is .maximum in- `ductance and maximum capacity but that by a proper design of the various elements, the ratio between the inductive reactance and the capacitance reactance may be mainta'ined subv-.Stantially Constant throughout this extremely wide frequency band. 'It Will-be appreciated that in ;this manner the inventor has accomplished the objects of his invention.

Althoug'h one embodiment .of the present invention has beendisclosed .and described herein :it is expressly understoond that various changes and substitutions may `be made therein without departing from the spirit of the inventionas Well understood by those skilled in the art. Reference therefore will be had to the appended claims for a definition of the limits of the invention.

The invention descr'ibedA herein may be manufactured and Vused by or for the Government of the United States of America .for governmental purposes withoutwthe payment :of any royalties f thereon or therefor;V i

What is claimed is: 1. In a high frequency circuit, a pair of con- 'denser stators, an inductance comprising a loop inated rotor is at right angles to the plane of 'said loop said condenser rotor is meshed with said stators, whereby there is provided a tank circuit having a very wide frequency range in :which the ratio of inductive reactance to capacitive reactance is maintained substantially con- ,stant as the total Circuit reactance is varied.

2. In a high frequency Circuit, a pair of condenser stators, an inductance Comprising a loop connecting said stators, a condenser rotor mounted for Cooperation with both of said stators, an

,inductance tuning means including a short-Cir-v cuited secondarymounted for rotation relative to said loop, and means simultaneously rotating 'said rotor and said short-circuited secondary in predetermined relation so that a tank Circuit L having a very wide frequency range is provided in which the ratio of inductive reactance to capacitive reactance is maintained substantially Constant as the total Circuit reactance is varied.

band connecting said stators and forming parallel inductive paths, a first rotor in capacitive coupling relation to said stators, a second rotor in inductive coupling relation to said band and means moving said rotors in uni-son to simultaneously vary said coupling relations.

4. A high frequency tuning unit comprising a pair of condenser stators, an annular metallic band connecting said stators and forming parallel inductive paths, capacitance tuning means including a rotor in capacitive relation to said stators, inductance tuning means including a laminated rotor in inductive relation to said band and means moving said rotors in unison for varying the ratio of inductive reactance to capacitive reactance in a substantially Constant manner.

5. A high frequency tuning unit comprising a pair of condenser stators, an inductance in the form of a loop connecting said stators, condenser tuning means capacitively Coupled to said stators, inductance tuning means inductively coupled to said loop, and means simultaneously varying in predetermined relation the coupling between said condenser tuning means and said stators and between said inductive tuning means and said loop.

6. A high frequency Circuit comprising a pair of condenser stators, an inductance in the form of a loop connecting said stators, condenser tuning means including a rotor mounted in variable capacitive coupling relation to said stators, inductance tuning means including a rotor mounted in variableinductive coupling relation to said loop, and means simultaneously rotating said rotors in predetermined relationship to vary the frequency of said Circuit while maintaining the ratio of inductive reactance to capacitive reactance substantially Constant.

7. A high frequency tuning unit comprising a pair of condenser stators, an inductance in the form of a loop connecting said stators, a rotatable tors, a condenser tuning means mounted on said shaft in capacitivev coupling relation to said stators, an inductance tuning means mounted on said shaft in inductive coupling relation with said loop, said condenser tuning means and said inductive tuning means relatively mounted on said shaft to provide maximum capacitive coupling relation when said inductance tuning means is in maximum inductive coupling relation to said loop, and means rotating said shaft to simultaneously vary said capacitive coupling relation and said inductive coupling relation.

8. In a high frequency Circuit, a pair of Condenser stators, an inductance comprising a loop connecting 'said stators, a rotatable shaft in a plane parallel to the plane of said loop and passing through said loop between said stators, a

'condenser rotor mounted on said shaft for cooperation with both of said stators, inductance tuning means including a short-circuited secondary mounted on said shaft in inductive coupling relation with said loop, said rotor and said shortcircuited secondary mounted on said shaft in predetermined relation so that the ratio of inductive reactance to capacitive reactance is maintained substantially Constant as the total Circuit lreactance is varied upon rotation of said shaft.

9. In a high frequency Circuit, a pair of Condenser stators, an inductance comprising a loop connecting said stators, a rotatable shaft in a plane parallel to the plane of said loop and passing through said loop between said stators, a condenser rotor mounted on said shaft for Cooperation with both of said stators, inductance tuning means including a short-circuited secondary mounted on said shaft in inductive coupling relation with said loop, said rotor and said short-Circuited secondary relatively mounted on said shaft so that the Circuit is tuned to maximum inductance when said rotor cooperates with said stators to provide maximum capacitance, and means rotating said shaft.

10. A high frequency Circuit comprising a pair of condenser stators, an inductance in the form of a loop connecting said stators, capacitance tuning means including a rotor mounted in variable capacitive coupling relation to said stators, inductance tuning means including a rotor mounted in variable inductive coupling relation to said loop, and means simultaneously varying said capacitive coupling relation and said inductive coupling relation to vary the frequency of said Circuit while maintaining the ratio of inductive reactance to capacitive reactance substantially Constant, the last named means including means for maintaining a predetermined relation between said rotors wherein the Circuit is tuned to maximum Capacitance when the inductance tuning means is in maximum inductive coupling relation with said loop.

11. In a high frequency circuit, a pair of Condenser stators, an inductance comprising a loop connecting said stators, a rotatable shaft in plane parallel to the plane of said loop and passing through said loop between said stators, a condenser rotor mounted on said shaft in capacitive coupling relation with said stators, a laminated rotor mounted on said shaft in inductive coupling relation with said loop, said condenser rotor and said laminated rotor mounted in such relation on said shaft so that said laminated rotor is in maximum coupling relation to said loop when said condenser rotor is in maximum coupling relation to said stators, and means rotating said 

